UKH

I've been looking at Google Earth, planning for an upcoming trip (Google Earth resolution in Snowdonia is amazing by the way, you can see every boulder).

I've spotted what appears to be a well constructed path leading SE up to the West face of Tryfan. I'm pretty sure it's not a stream, but it's not marked on the OS maps. It appears to lead to the base of the large scree slope in the gully between the main and north summits.

Scrambles in Snowdonia doesn't list any routes here, and it seems like walking up the scree slope would be a bad idea. So

1) Why is there a path here? Who uses it?

2) Why isn't it listed on the OS map if it's a deliberately constructed path?

Think that’ll be the West Face route, often used in descent as it’s the quickest way off. Tops out between the two summits. Grass/mud on the bottom section, then a made path, then an easy scramble, but loose.

It's certainly not the grade 3 "West Face Route" listed in Scrambles in Snowdonia: the one I'm talking about is a few hundred metres further south than the Notch. That doesn't necessarily contradict what you're saying though.

The OS may have made a judgement on it along the lines of as far as most walkers are concerned its not a viable route so they've just shown the main routes up and down the mountain (+ the definitive public rights of way) 

No, not that, I shouldn’t have called it the West face route. The route I’ve described is up the West flank of Tryfan, barely a grade 1 at the top. It’s a very common route up or down

The path is marked on the Harvey's 1:40,000 and is a fair descent. Steve

I’ve scooted off down there before and it’s not easy but is quite a direct way down. 

It's a grim and loose way up when the other easy scrambles are all good. It's a fast descent if happy with loose stuff.

That's the Western Gully "path," it's the easiest and quickest way on/off the summit.

1philjones1's description is spot on. The path is easily spotted from the road and is best accessed from the first lay-by or car park. I've descended it plenty of times having watched the sunset from the summit, personally I've never found it grim or loose.

In descent that is the fast way off Tryfan for fell runners, it's quite a steep kind of gully and not particularly pleasant TBH! After the top gully section you can either continue down the path you mention or turn right and take the gully nearest Tryfan if you want to come out on the road near the end of Llyn Ogwen

Blimey, the OP ain't wrong.... you can see every boulder, even Adam & Eve.

When we were students bumbling around on Tryfan we came across a huge boulder cave somewhere on the NW flank of the mountain. I've never been able to find it again. 

The Google maps 3D view of Snowdonia is very good. I used it to virtual recce Llanberis to Capel Curig for a friends Paddy Buckley found I was supporting on!

The western gully descent is indeed fast. 

If I recall correctly the summit to A5 record was set (Beard or Donnelly, can't recall) at 4 minutes!

b